Polyolefins stabilized with acylated diarylphosphinodithioates



United States Patent 3,475,370 POLYOLEFINS STABILIZED WITH ACYLATED DIARYLPHOSPHINODITHIOATES Silvio L. Giolito, Whitestone, N.Y., assignor to Stautfer Chemical Company, New York, N.Y., a corporation of Delaware No Drawing. Original application Oct. 23, 1965, Ser. No. 504,243. Divided and this application Dec. 5, 1967, Ser.

Int. Cl. C08f 45/58, 3/10 US. Cl. 26045.7 9 Claims ABSTRACT OF THE DISCLOSURE Poly-wolefin compositions having improved light stability. The compositions comprise an u-olefin polymer formed by the polymerization of an a-mono-olefinic aliphatic hydrocarbon having from 2 to 10 carbon atoms and a stabilizing quantity of a novel acylated diphenylphosphinodithioate of the general formula:

wherein X, R and R are as previously defined and n is an integer of from 1 to 10.

This application is a division of application No. 504,243 filed Oct. 23, 1965.

This invention relates to organophosphorous esters. More particularly, this invention is concerned with acylated diphenylphosphinodithioates which are useful as light (ultraviolet) stabilizers for poly-alpha-olefin compositions.

It is known that plastic and polymeric materials generally undergo degredation in the presence of light and/ or heat. Especially sensitive to these agencies are some of the synthetic resins such as polyethylene, polypropylene and the like. In order to increase the life of plastics and polymers, it has become the practice to incorporate therein certain substances, usually referred to as ultraviolet absorbers which are capable of absorbing the incident actinic radiation, thereby protecting the plastic substrate from deterioration.

We have now discovered that certain acylated diphenylphosphinodithioates are eifective in protecting poly-alphaolefins against the deleterious efiects of light, and the provision of such compounds constitutes the primary purpose and object of this invention.

Another object of the invention is to provide polyalpha-olefin compositions stabilized with the abovenamed compounds.

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Other objects will be apparent from the detailed description which follows.

The novel acylated diphenylphosphinodithioates of the invention may be represented by the general formula it if R-P-S-C-R wherein R and R are aromatic hydrocarbon groups such as phenyl, naphthyl and the like which may be substituted, such as chlorophenyl, lower alkylated phenyl, lower alkoxy phenyl and the like; X is a chalcogen such as oxygen and sulfur, and R is an alkyl of from 1 to 20 carbon atoms, and aromatic hydrocarbon radical such as phenyl, naphthyl and the like which may be chloro substituted, an aralkyl such as benzyl or a radical selected from the formulae consisting of wherein X, R and R are as previously defined, and n is an integer of from 1 to 10.

Specific compounds falling within the ambit of the above formula include the following:

i i @P-S-C-CIIz-Clia The novel compounds of the invention are prepared by reacting a diarylphosphinodithioate with an acyl chloride in accordance with the following equation:

wherein R, R X and R are as previously defined and M is a metallic cation such as sodium or potassium.

In preparing the new organophosphorous esters of the invention, I have discovered that generally excellent results are achieved by heating the diphenylphosphinodithioate with an acyl halide with or without a solvent and thereby isolating the acylated diphenylphosphinodithioate from the alkali metal chloride by-pnoduct. An especially convenient means for conducting the reaction is to reflux the components in the presence of a relatively inert organic solvent such as the lower ketones which include acetone, methyl ethyl ketone and diethyl ketone. The use of a catalyst is also desirable such as methylamine, diethylamine and pyridine. After removing the alkali metal chloride by-product and distilling off the solvent, the residual acylated diphenylphosphinodithioate may be isolated by employing the usual techniques available to the skilled organic chemist such as crystallization, distillization, sublimation and the like.

The ultraviolet stabilizers contemplated by the invention may :be blended or incorporated into the poly-alphaolefin compositions by any of the conventional methods commonly used for mixing such materials with resins and plastics. For example, milling on heated rolls, deposition from solvents and dry blending are well-known techniques.

In order to prepare poly-alpha-olefin compositions which are resistant to prolonged exposure to sunlight and the elements, it is preferred that the concentration of the novel acylated diphenylphosphinodithioate be maintained in the range of 0.01 to about 5.0% based on the weight of the polymer.

Although the molecular weight of poly-alpha-olefins varies over wide limits, the compounds of the invention are not restricted to any particular molecular weight range. Poly-alpha-olefins ranging in molecular weight from about 15,000 to about 20,000, however, are afforded particularly excellent protection.

The following examples which are illustrative of the invention should not be construed as limiting examples, for variations and modifications thereof will be apparent to one having ordinary skill in this art.

PREPARATION OF THE COMPOUNDS Example 1.Benzoyl diphenylphosphinodithioate 27.2 grams (0.1 mole) of sodium diphenylphosphinodithioate were dissolved in 200 milliliters of acetone to which was added slowly 14.0 grams (0.1 mole) of benzoyl chloride. The reaction mixture was then refluxed for two hours during which time a precipitate of sodium chloride separated out. The mixture was filtered to remove the sodium chloride salt and the filtrate distilled at reduced pressure to remove the acetone and other volatile materials. Benzene was next added, the mixture warmed to dissolve the crystals, washed once with dilute sodium hydroxide, filtered, separated, washed once with water, separated, dried over charcoal, and flash evaporated under reduced pressure to remove the benzene. Aiter standing over night, the white crystals which formed were crystallized from a mixture of hexane and benzene to yield a purified benzoyl diphenylphosphinodithioate having an analysis of 17.9% S (calculated 17.9% S) and a melting point of 120-l C.

Using the procedure of Example 1, the following compounds were synthesized.

4 Example 2.Propionyl diphenylphosphinodithioate brown oil ND24:1.6241 Example 3.Acetyl diphenylphosphinodithioate white crystals; llLP. 86-90 C. Example 4.Keto bis(diphenylphosphinodithioate) red oil ND'24:1.62G7

Example 5.Sebacoylketo bis(diphenylphosphinodithioate) 5 O i yellow oil ND24=1.6376 Example 6.Isovaleryl diphenylphosphinodithioate o GP-s-ii-(mwm),

brown oil ND24=1 6313 Example 7.-Lauroyl diphenylphosphinodithioate s 0 Q II II brown oil P-S-C (CH2)10-CH3 Example 8.Caproyl diphenylphosphinodithioate ll QP-S-C-(CHDr-CH;

brown oil Xenon Arc Weatherometer operating at 6000 watts. The water cycle was adjusted whereby each sample was subjected to 18 minutes of water spray and 102 minutes of dry exposure for each two hours of exposure. Exposure damage to the samples of polypropylene was assessed with respect to change of structural strength.

After a period of exposure in excess of 900 hours, the test sheet of polypropylene showed no signs of brittleness to 180 flexure test. Nor was there any evidence at this time of any surface crazing or any coloration or staining. A blank specimen of unstabilized polypropylene which was exposed concurrently with the stabilized product failed the flexure test after 250 to 300 hours exposure time.

The Weatherometer as used in compiling the data and tests described herein was purchased from the Atlas Electric Devices Company, Chicago, Illinois. The instrument is identified as a 6000 watt Xenon Arc Weatherometer Model 60W.

The polypropylene resin as used in the above-described example is an unstabilized general purpose, high molecular weight polypropylene of the isotactic or crystalline type. Typically, it has a melt index of 4 at 230 C. and a specific gravity of 0.905. The resin was purchased from the Hercules Powder Company under the trade-name Profax and further identified as number 6501, type P- 02004 and is supplied in the form of natural flakes. We have also used other commercially available grades of unstabilized isotactic polypropylene resin, and in this connection, mention is made of unstabilized Avisun polypropylene (Avisun Corp.) and unstabilized Shell polypropylene (Shell Chemical Co., Division of Shell Oil). The results obtained in using the various grades and types of polypropylene were in general agreement.

I claim:

1. A solid poly-alpha-olefin composition having improved stability toward light degradation which comprises an alpha-olefin polymer formed by the polymerization of an alpha-monoolefinic aliphatic hydrocarbon having from 2 to carbon atoms and a stabilizing quantity of a novel acylated diphenylphosphinodithioate of the general formula wherein R and R are each selected from the group consisting of phenyl, chloro-substituted phenyl, naphthyl, lower alkylated phenyl and lower alkoxy phenyl; X is a chalcogen selected from the group consisting of oxygen and sulfur; and R is selected from the group consisting of alkyl having from 1 to 20 carbons, phenyl, naphthyl, chloro-substituted phenyl, benzyl and a radical selected from the formulae wherein X, R and R are as previously defined and n is an integer of from 1 to 10.

2. A solid poly-alpha-olefin composition according to claim 1 having improved stability toward light degradation which comprises solid polypropylene and about 0.01% to about 5.0%, based on the polypropylene of benzoyl diphenylphosphinodithioate.

3. A solid poly-alpha-olefin composition according to claim 1 having improved stability toward light degradation which comprises solid polypropylene and about 0.01% to about 5.0%, based on the polypropylene of propionyl diphenylphosphinodithioate.

4. A solid poly-alpha-olefin composition according to claim 1 having improved stability toward light degradation which comprises solid polypropylene and about 0.01% to about 5.0%, based on the polypropylene of a-cetyl diphenylphosphinodithioate.

5. A solid poly-alpha-olefin composition according to claim 1 having improved stability toward light degradation whichl comprises solid polypropylene and about 0.01% to about 5.0%, based on the polypropylene of keto bis (diphenylphosphinodithioate).

6. A solid poly-alpha-olefin composition according to claim 1 having improved stability toward light degredation which comprises solid polypropylene and about 0.01% to about 5.0%, based on the polypropylene of sebacoyl keto bis (diphenylphosphinodithioate).

7. A solid poly-alpha-olefin composition according to claim 1 having improved stability toward light degredation which comprises solid polypropylene and about 0.01% to about 5.0%, based on the polypropylene of isovaleryl diphenylphosphinodithioate.

8. A solid poly-alpha-olefin composition according to claim 1 having improved stability toward light degradation which comprises solid polypropylene and about 0.01% to about 5.0%, based on the polypropylene of lauroyl diphenylphosphinodithioate.

9. A solid poly-alpha-olefin composition according to claim 1 having improved stability toward light degredation which comprises solid polypropylene and about 0.01% to about 5.0%, based on the polypropylene of caproyl diphenylphosphinodithioate.

References Cited UNITED STATES PATENTS 3,314,917 4/1967 Herbstman 260-457 3,419,523 12/1968 Herbstman 26045.85

DONALD E. CZAJA, Primary Examiner R. A. WHITE, Assistant Examiner 

